Air impulse apparatuses or air guns for use in water well rehabilitation are widely known. In theory, these apparatuses should be usable for stimulating and improving hydrocarbon flow in oil, gas or coal bed-methane (CBM) bearing rock formations. In practice, however, these apparatuses have only rarely been used for oil and gas well completion, stimulation and maintenance, despite the fact that the fossil fuel energy industry could benefit from the application of such technology.
Current methods for stimulating hydrocarbon flow in oil, gas, or CBM rock formations are based on conventional hydrofracturing techniques. These require pumping a liquid into an oil, gas or CBM well at a pressure and flow rate high enough to split the rock and to create cracks in the rock formation around the borehole (wellbore). The hydrostatic pressure increases slowly until the resistance of the rock is overcome and the formation's fracturing pressure is reached. The pressure applied in conventional hydrofracturing is non-cyclic.
Some prior art fracturing techniques for oil wells include using a gas impulse device to assist in well stimulation. However, current fracturing techniques using such devices are not entirely satisfactory when applied to oil, gas or CBM wells. They are also unsatisfactory for stimulating water wells. For example, one apparatus and method used does not provide enough energy to extend the fractures within an oil or gas bearing formation out to reasonable distances from the wellbore. Fractures that have been opened after firing the gas impulse apparatus tend to close after the impulse is spent. The gas impulse device must then reopen the same fractures after each firing without the length of the fracture substantially increasing.
Some oil well fracturing techniques when employing a gas impulse device produce very little effect, since most of the energy provided by the impulse device is dissipated in displacing a fluid column in the wellbore and in overcoming the resistance of the wellbore-formation face.
There is therefore a need in the fossil fuel energy industry for a more efficient method for stimulating and improving hydrocarbon flow in oil, gas and CBM wells, when using gas impulse devices.